Proportional pressure-regulator valve

ABSTRACT

A proportional pressure-regulator valve comprising a load-dependent control step and a method for the load-dependent regulation of a pressure level of a pressure medium with one proportional pressure-regulator valve. The load-dependent control step is obtained with a proportional magnet ( 1 ) having at least two gaps ( 10, 12 ) for regulating the magnetic force. The size of the gaps ( 10, 12 ) can be adjusted independently of each other. While a first gap (! 2 ) is current-dependent regulated, the size of the second gap ( 10 ) can be regulated via a pressure force adaptable in proportion to a load requirement in the hydraulic circuit.

[0001] According to the preamble of claim 1, the instant inventionrelates to a proportional pressure-regulator valve. The inventionfurther covers, according to the preamble of claim 17, a method forregulating a pressure level of a pressure medium with a proportionalpressure-regulator valve.

[0002] In a transmission, particularly an automatic transmission of amotor vehicle, the pressure is regulated in a hydraulic circuitaccording to requirements. While for the supply of lubricating oil tothe parts of the transmission, the pressure level can be kept low in ahydraulic circuit, during the shifting operations the pressure has to besharpy raised in order, for example, to be quickly able to fill shiftingelements.

[0003] According to the prior art, there have been used for regulatingthe pressure in hydraulic circuits pressure regulators which controlshift valves for actuating the clutch. The shift valves are controlledwithin the pressure regulator by means of a proportional magnetconsisting, among other elements, of a magnetic core, a magnetic coiland a magnetic armature. The proportional magnet controls here the coilcurrent proportionally to an output variable force, that is, accordingto the coil current the magnetic armature and therewith the shift valveare controlled for actuating the clutch. From the resultingcharacteristic magnetic force-current characteristic lines of thepressure regulator are produced in an electrohydraulic control ofautomatic transmissions the pressure-current characteristic linesdesired for clutch adaptation.

[0004] In the Applicant's German Patent Application DE 100 03 896 A1, apressure regulator is described which adjusts as needed a shift valve bymeans of a stationary proportional magnet, a magnetic coil, a movablemagnetic armature and a specific control system thus regulating thepressure in the hydraulic circuit. The pressure-current characteristicline has a curve continuously rising from the start on, that is, as thecurrent force increases so increases the pressure also. But in thepractice, the gradient of the pressure-current characteristic line is inoperation too large for the requirements so that the pressure-currentcharacteristic line is too steep and thereby the current sensitivity ofthe pressure regulation is not enough for a comfortable gear ratio. Incase of a low load, that is, at low pressures, the low sensitivity makesitself noticeable specifically in a poor shifting quality.

[0005] Therefore, the invention is based on the problem of overcomingthe disadvantages of the prior art and, in particular, of providing aproportional pressure-regulator valve for regulating a pressure level ina hydraulic circuit and of outlining a method by which the changes ofpressure level in a hydraulic circuit are adjusted to be as comfortableas possible and showing how such a proportional pressure-regulator valveis controlled.

[0006] The problem on which the invention is based is solved by aproportional pressure-regulator valve having the features of claim 1 anda method of regulating a pressure level in a hydraulic circuit with aproportional pressure-regulating valve having the features of claim 17.

[0007] The requirement of a high pressure-current sensitivity, above allin the low-pressure range, is satisfied by a load-dependent adaptationof the pressure-current characteristic line, herebelow called a p-Icharacteristic line for the sake of simplicity.

[0008] The load-dependent adaptation of the p-I characteristic line ofthe inventive proportional pressure-regulator valve is implemented by aproportional magnet having two gaps that can be controlled independentlyof each other. The first gap is part of an immersion step known from theprior art which is controlled by means of induced magnetic field. Saidmagnetic field is produced by an electric current in the magnetic coil,it then proceeds via the magnetic armature existing in the interior ofthe magnetic coil, the housing and the magnetic core. An axialseparation between the magnetic armature and the magnetic core by meansof a non-magnetic ring results in that the magnetic field can pass overto the magnetic armature only via a radial gap. At this point, themagnetic field produces a magnetic force that acts upon the magneticarmature and moves it in axial direction depending on the magneticforce. A continuous electric control respectively of the proportionalmagnet and of the magnetic coil in this manner makes possible acontinuous control respectively of the magnetic armature and of acontrol element connected by an armature rod with the magnetic armature.

[0009] According to the invention, there is additionally obtainedrespectively via a second gap and a second immersion step, a targetedweakening of the magnetic field. The second gap is implemented by usingan inventive magnetic core consisting of at least two parts,specifically a first and a second part.

[0010] The first part of the magnetic core is firmly connected with thehousing, located concentrically and axially movable around the armaturerod fixedly connected with the magnetic armature. The first part of themagnetic core projects partly into the interior of the magnetic coil.

[0011] The second part of the magnetic core is, likewise coaxially,concentrically and axially movably disposed around the armature rod. Butthe second part, contrary to the first part firmly connected with thehousing, is axially freely movable. The second part of the magnetic coreis, therefore, implemented in the manner of a sliding part which issituated adapted to be laid on the first part and preferably providedaxially between the first part of the magnetic core and the housing.

[0012] This division of the magnetic core in a first part firmlyconnected with the housing and a second part axially movably disposedmakes possible an adjustment of the width of the second gap which can beformed between said two parts.

[0013] Thus is made possible a control as needed of the second gap. Thesecond gap constitutes, like the first gap, a magnetic resistance in themagnetic circuit. The larger said gap widths are, the greater themagnetic resistance and weaker the magnetic field in the magneticcircuit. The position of the second part of the magnetic core whichdetermines the size of the second gap, therefore, affects the magneticresistance in the magnetic circuit and consequently the strength of themagnetic field.

[0014] This means that, for example, a large second gap altogetherweakens the magnetic field and thus the magnetic force is reducedbetween the first part of the magnetic core and the magnetic armature.The regulation, via the electric current on the magnetic coil in thiscase, is less sensitive on account of the high magnetic resistance. Thegradient of the p-I characteristic line is then smaller than in a smallsecond gap, which means that the current sensitivity of the pressureadjustment is lower and thus is given a high cancellation of thepossibility of pressure adjustment. This advantageously takes effectabove all in the low-pressure range, since in this range changes ofpressure are particularly detectable.

[0015] The first and the second part of the magnetic core advantageouslyhave corresponding contact surfaces the design of which in the secondgap produces a radial magnetic crossing of field line between the secondand the first part of the magnetic core.

[0016] The second part of the magnetic core is preferably implemented bya conic shift valve. The shape of the cone has a great influence uponthe properties of the proportional magnet. The cone angle determines theportion of the radial and axial forces that can be transmitted by themagnetic flow to the shift valve and to the second part of the magneticcore. The radial forces level over the periphery. A high portion thereofis therefore to be sought. But axial forces are also needed in order toeffect a stroke-dependent magnetic flow change. The axial forces should,of course, be as weak as possible, since otherwise a second regulationpoint generates and non-linearities can appear in the p-I behavior ofthe proportional pressure-regulator valve. This would result in negativeregulation quality. Besides, a working point in the characteristic fieldwould not be clearly adjustable having two regulation points. Theproportional magnet should, therefore, be regulated mainly via the firstgap. Furthermore, the influence of the second gap should be certain fromthe point of view of regulation technology.

[0017] The second magnet core is controlled by a pressure force which ispreferably hydraulic but can also be produced pneumatically ormechanically. The pressure force advantageously adjusts itself accordingto a load requirement in the transmission, especially in case of ahydraulic control depending on a hydraulic pressure in the hydrauliccircuit. The hydraulic pressure as command variable for control of thesecond gap is either the main pressure itself, a pressure proportionalto the main pressure, or the issued pressure proper.

[0018] With the dependence of the pressure force on the load requirementin the transmission, a proportional lowering of the p-I characteristicline is possible in the partial load range.

[0019] Summarizing, the inventive proportional pressure-regulator valvecan be shown with the following advantages.

[0020] The inventive proportional pressure-regulator valve and methodmake possible two effective engagement parameters independently of eachother for the control of a pressure level, especially of a gear clutchpressure. The reduced gradient of the p-I characteristic line in thepartial load range produces the increase of sensitivity of the p-I.

[0021] If the issued pressure is used as command variable for thecontrol of the second gap, it is possible to obtain a high p-Isensitivity in the low-pressure range and a correspondingly lowsensitivity in the high-pressure range.

[0022] In a development of the invention, it is provided that thepressure force is axially passed into the second part of the magneticcore via a shift valve. Said shift valve can be laid non-positively onthe second part of the magnetic core and preferably has the shape of ahollow cylindrical sleeve which has a substantially annular pressuresurface. Said pressure surface is connected with a feed line of thehydraulic circuit and, therefore, can be loaded with a hydraulicpressure force. The shift valve is thus actuated by a hydraulic pressureproportional to a load requirement in the hydraulic circuit.

[0023] This means that the second gap is controlled depending on loadand thus respectively the magnetic field and the magnetic force betweenmagnetic armature and the first part of the magnetic core are influenceddepending on load.

[0024] In one other development of the invention, it is provided thatthe hydraulic control of the second gap be ensured via several axialholes. The shift valve does not sit directly upon the armature rod buton the pole core. The system thereby acquires a stable behavior, sincethe width-to-height ratio is considerably improved. Besides, thiscontrol also makes an accurate positioning of the second part of themagnetic core possible.

[0025] For better understanding the invention is now explained withreference to an embodiment and to a p-I characteristic line shown in theenclosed drawings where:

[0026]FIG. 1 is a longitudinal section of a proportional magnet with ahydraulic control of the second air gap; and

[0027]FIG. 2 is a p-I characteristic line field of the inventiveproportional pressure-regulator valve.

[0028] In FIG. 1 is shown a longitudinal section of a proportionalmagnet 1. The proportional magnet 1 consists, among other elements, ofone magnetic coil 4, one magnetic armature 3 movable in the interior ofthe magnetic oil, one armature rod 5 fixedly connected with the magneticarmature 3 and a two-part magnetic core. The magnetic core has one firstpart 2 and one second part 6. Both parts 2, 6 are disposed coaxially,concentrically and movably relative to the armature rod 5. While thefirst part 2 is firmly connected with the housing 11, the second part 6is provided axially movable in the proportional magnet 1. If an electriccurrent flows into the magnetic coil 6, a magnetic field is generatedwhose magnetic flow passes into a magnetic circuit via the housing 11,the magnetic core and the magnetic armature 3. At the same time, thereis a magnetic source generated in a first gap 12 between the first partof the magnetic core 2 and the magnetic armature 3, which attracts themagnetic armature 3. The consequence of said movement of the magneticarmature 3 is an actuation of the control element via the armature rod5.

[0029] With the second part of the magnetic core 6, a second gap 10 canbe adjusted in the magnetic circuit which, depending on its magnitude,constitutes a magnetic resistance. The larger the second gap 10 is, thelarger the magnetic resistance in the magnetic circuit and the smallerthe magnetic flow. The consequence of the change of the magnetic flow isdirectly a change of the magnetic force in the first gap 12 and,therefore, also respectively effects upon the movement of the magneticarmature 3 and the actuation of the control element.

[0030] The second part of the magnetic core 6 is moved by a pressureforce. In the embodiment shown, the pressure force resultshydraulically. A shift valve 13, which can be non-positively laid on thesecond part of the magnetic core 6, guides the pressure force axiallyinto the second part of the magnetic core 6. The shift valve 13 isdesigned as hollow cylindrical sleeve which is located in a hole of thehousing 11 and seals it as oil tight as possible. Said shift valve 13provides a pressure surface which with a feed line 16 is connected tothe hydraulic circuit which thereby is loaded with a hydraulic pressureforce. The hydraulic pressure force corresponds here to the mainpressure or is proportional to the main pressure or is the issuedpressure proper. The actuation of the second part of the magnetic core 6is thus dependent on a load requirement which reflects itself in thepressure level in a hydraulic circuit. There is further provided in thehousing 11 a breather hole 15 in order to ventilate the space formed bythe shift valve 13, the second part of the magnetic core 6 and thehousing 11 and to discharge from the interior of the housing leakage oilthat eventually appears.

[0031] A pressure spring 9 between the first part 2 and the second part6 of the magnetic core again resets the second part of the magnetic core6 as soon as the hydraulic force is reduced.

[0032] There is also provided a non-magnetic disc 17 which, on one hand,firmly connects the first part of the magnetic core 2 with the housingand, on the other, diverts the magnetic flow so that it has to flowfirst via the second part 2, then via the first part of the magneticcore 6.

[0033] This geometry ensures that the magnetic flow has to flow via twogaps 10, 12 the size of which can be influenced independently of eachother. Thus the magnetic force, which ultimately produces respectivelythe movement of the magnetic armature 3 and the actuation of the controlelement, is adjusted by two parameters determinable independently ofeach other.

[0034] The first adjustable parameter is here the current strength inthe magnetic coil 4 and the second parameter a variable adaptedaccording to the load requirement, for example, the hydraulic pressurein a hydraulic circuit. The combination of said two parameters makespossible the load adaptation of a control for a proportional magnet andachieves a favorable pressure-current sensitivity in a desired range ofpressure.

[0035] In FIG. 2 is shown a characteristic line field with three p-Icharacteristic lines. The characteristic line a represents the p-Icharacteristic line with maximum size of the second gap 10,characteristic line b the p-I characteristic line with minimum size ofthe second gap 10 and characteristic line c the p-I characteristic linewith the individual output pressure as commanding variable.

[0036] In the comparison of the characteristic lines a and b can beclearly understood that the gradient of the characteristic line b islarger than that of the characteristic line a. Therefrom is to beinterpreted that the p-I sensitivity depends on the size of the secondgap 10 and this in a manner such that the p-I sensitivity increases asthe size of the second gap 10 increases.

[0037] The characteristic line c shows a p-I sensitivity initially of amagnitude similar to the characteristic line a. But starting from acertain value it proceeds more abruptly and approximates the curve ofcharacteristic line b. Therefore, with the individual output pressure ascommand variable, a large p-I sensitivity can be achieved in thelower-pressure range and a reduced p-I sensitivity in the high-pressurerange.

[0038] Reference Numrals

[0039]1 proportional magnet

[0040]2 first part of the magnet core

[0041]3 magnetic armature

[0042]4 magnetic coil

[0043]5 armature rod

[0044]6 second part of the magnetic core

[0045]7 contact surface of the first part of the magnetic core

[0046]8 contact surface of the second part of the magnetic core

[0047]9 pressure spring

[0048]10 second gap

[0049]11 housing

[0050]12 gap

[0051]13 shift valve, sleeve

[0052]14 pressure surface

[0053]15 breather hole

[0054]16 feed line

[0055]7 non-magnetic disc

1. Proportional pressure-regulator valve for regulating a pressure levelin a hydraulic circuit, comprising one armature rod (5) as connectionbetween one control element situated in the hydraulic circuit and theproportional magnetic (1) in one housing (11) which consists of onemagnetic core, one magnetic armature (3) and one magnetic core (4)wherein said magnetic coil (4) and said magnetic core are firmlyconnected with said housing (11) and in the interior of said magneticoil (4) said magnetic armature (3) can be moved back and forth axiallybetween two end positions by a magnetic force existing within one gap(12) between said magnetic armature (3) an said magnetic core and saidmagnetic core partly projects into the interior of said magnetic coil(4) and at the same time is situated concentrically an axially movablyaround said armature rod (5) firmly connected with an end of saidmagnetic armature (3) and the motion of said magnetic armature (3)results in an actuation of said control element, characterized in thatsaid proportional magnet (1) has a second adjustable gap (10) forregulating the magnetic force.
 2. Proportional pressure-regulator valveaccording to claim 1, characterized in that said magnetic core consistsof at least one first part (2) and one second part (6) providedcoaxially with said armature rod (5).
 3. Proportional pressure-regulatorvalve according to claim 1 or 2, characterized in that said second partof said magnetic core (6) is provided axially between said first part ofsaid magnetic core (6) and said housing (11) forming a second adjustableair gap (10) for said first part of said magnetic core (2). 4.Proportional pressure-regulator valve according to any one of thepreceding claims, characterized in that said first part of said magneticcore (6) is disposed axially movably and concentrically around saidarmature rod (5) and the motion of said second part of said magneticcore (6) results from a pressure force.
 5. Proportionalpressure-regulator valve according to any one of the preceding claims,characterized in that to produce the pressure force, one shift valve(13), which can be non-positively laid on said second part of saidmagnetic core (6), is provided and the pressure force is axially passedvia said shift valve (13) to said second part of said magnetic core (6).6. Proportional pressure-regulator valve according to any one of thepreceding claims, characterized in that said shift valve (13) is made ofnon-magnetic material and is axially movably and concentrically disposedaround said armature rod (5).
 7. Proportional pressure-regulator valveaccording to any one of the preceding claims, characterized in that thepressure force can be produced hydraulically, pneumatically, ormechanically.
 8. Proportional pressure-regulator valve according toclaim 7, characterized in that said shift valve (13) is actuated inproportion respectively to a load requirement and a hydraulic pressurein the hydraulic circuit.
 9. Proportional pressure-regulator valveaccording to any one of the preceding claims, characterized in that saidshift valve (13) is designed as hollow cylindrical sleeve which islocated in one hole of said housing (11) and seals it as oil-tight aspossible.
 10. Proportional press-regulator valve according to claim 9,characterized in that said shift valve (13) has on one front side asubstantially annular pressure surface which is connected with a feedline (16) of the hydraulic circuit and can be loaded with a hydraulicpressure force.
 11. Proportional pressure-regulator valve according toany one of the preceding claims, characterized in that said second part(6) and said first part (2) of said magnetic core have correspondingcontact surfaces (7, 8) the design of which in the second gap (10)produces a radial magnetic field line crossing between said second part(6) and said first part (2) of said magnetic core.
 12. Proportionalpressure-regulator valve according to any one of the preceding claims,characterized in that said contact surface (7) of said first part ofsaid magnetic core (2) is situated upon an outer cone.
 13. Proportionalpressure-regulator valve according to any one of the preceding claims,characterized in that said contact surface (8) of said second part (6)of said magnetic core is designed upon an inner cone.
 14. Proportionalpressure-regulator valve according to any one of the preceding claims,characterized in that in said housing (11) a breather hole (15) isprovided which ventilates the space formed by said shift valve (13),said second part of said magnetic core (6) and said housing (11). 15.Proportional pressure-regulator valve according to any one of thepreceding claims, characterized in that between said second part (6) andsaid first part (2) of said magnetic core (6), concentrically with saidarmature rod (5), one pressure spring (9) is disposed which produces aspring tension between respectively said second part (6) and said firstpart (2) of said magnetic core and said shift valve (13) and said springtension counteracts the hydraulic pressure force.
 16. Proportionalpressure-regulator valve according to any one of the preceding claims,characterized in that a non-magnetic disc (17) is provided which firmlyconnects first part of said magnetic core (2) with said housing (11).17. Method for regulating a pressure level in a hydraulic circuit withone proportional pressure-regulator valve comprising one armature rod(5) for connecting a control element located in the hydraulic circuitwith one proportional magnetic which consists of one magnetic core, onemagnetic armature (3) and one magnetic coil (4) said magnetic armature(3) being axially movable back and forth between two end positions by amagnetic force existing in an air gap (18) and the magnetic forcedepending on a magnetic flow in a magnetic circuit which is adjustableby the height of an electric current laid on said magnetic coil (4),characterized in that a magnetic core is used which consists of at leastone first part (2) and one second part (6) whereby in the magneticcircuit a second gap (10) can be created so that a magnetic resistancegenerates which regulates the magnetic force.
 18. Method according toclaim 17, characterized in that said second gap (10) is adjustable bymoving a second part of said magnetic core (6) coaxially with saidarmature rod (5).
 19. Method according to claim 17 or 18, characterizedin that said second part of said magnetic core (6) is movable by meansof a shift valve (13) which is actuated hydraulically, pneumatically ormechanically.
 20. Method according to any one of claims 17 to 19,characterized in that said shift valve (13) can be actuated by ahydraulic pressure proportional to a load requirement in the hydrauliccircuit and thus the magnetic force can be adjusted depending on theelectric current flowing into said magnetic coil (4) and the loadrequirement in the hydraulic circuit.
 21. Method according to any ofclaims 17 to 20, characterized in that as the width of said air gap (10)diminishes, the magnetic resistance in the magnetic circuit becomesweaker and thus the magnetic force can be adjusted between said firstpart of said magnetic core (2) and magnetic armature (3).
 22. Methodaccording to any one of claims 16 to 20, characterized in that betweensaid second part (6) and said first part (2) of said magnetic core onepressure spring (9) is situated which as the hydraulic force diminisheson said second part of said magnetic core (6), the latter moves awayfrom said first part of said magnetic core (2) so that said second gap(10) between said part (6) and first part (2) of the magnetic corebecomes enlarged and the magnetic force diminishes.